A fast, green and readily reproducible microwave-based method for the production of high quality silver nanoparticles （AgNPs） in high yield is presented. Starch is used as a stabilizing agent with few pentose differ...A fast, green and readily reproducible microwave-based method for the production of high quality silver nanoparticles （AgNPs） in high yield is presented. Starch is used as a stabilizing agent with few pentose different reducing carbohydrates as D-ribose, D-arabinose and L-arabinose. From the UV-vis peak profile spectra of the solutions of the silver nanoparticles, the authors have investigated the size of the NPs together with the average diameter, shape, and aggregation state of the colloidal AgNPs. TEM measurements and EDX analysis have confirmed the morphology of our AgNPs.展开更多
First passage time in Markov chains is defined as the first time that a chain passes a specified state or lumped states. This state or lumped states may indicate first passage time of an interesting, rare and amazing ...First passage time in Markov chains is defined as the first time that a chain passes a specified state or lumped states. This state or lumped states may indicate first passage time of an interesting, rare and amazing event. In this study, obtaining distribution of the first passage time relating to lumped states which are constructed by gathering the states through lumping method for a irreducible Markov chain whose state space is finite was deliberated. Thanks to lumping method the chain＇s Markov property has been preserved. Another benefit of lumping method in the way of practice is reduction of the state space thanks to gathering states together. As the obtained first passage distributions are continuous, it may be used in many fields such as reliability and risk analysis展开更多
With respect to the different hydrological responses of catchments, even the adjacent ones, in mountainous regions, there are a great number of motivations for classifying them into homogeneous clusters. These motivat...With respect to the different hydrological responses of catchments, even the adjacent ones, in mountainous regions, there are a great number of motivations for classifying them into homogeneous clusters. These motivations include prediction in ungauged basins(PUB), model parameterization, understanding the potential impact of environmental changes, transferring information from gauged catchments to the ungauged ones. The present study investigated the similarity of catchments through the hydro-climatological pure time-series of a 14-year period from 2001 to 2015. Data sets encompass more than 13,000 month-station streamflow, rainfall, and temperature data obtained from 27 catchments in Utah State as one of the eight mountainous states of the USA. The identification, analysis, and interpretation of homogeneous catchments were investigated by applying the four approaches ofclustering, K-means, Ward, and SOM(Self-Organized Map) and a newly proposed Wavelet-Entropy-based(WE-SOM) clustering method. By using two clustering evaluation criteria, 3, 5, and 6 clusters were determined as the best numbers of clusters, depending on the method employed, where each cluster represents different hydro-climatological behaviors. Despite the absence of geographic characteristics in input data matrix, the results indicated a regionalization in agreement with topographic characteristics. Considering the dependency of the hydrological behavior of catchments on the physiographic field aspects and characteristics, WE-SOM method demonstrated a more acceptable performance, compared to the other three conventional clustering methods, by providing more clusters. WE-SOM appears to be a promising approach in catchment clustering. It preserves the topological structure of data which can, as a result, be proofed in a greater number of clusters by dividing data into higher numbers of distinct clusters withsimilar altitudes of catchments in each cluster. The results showed the aptitude of wavelets to quantify the time-based variability of temperature, rainfall and streamflow, in the way contributing to the regionalization of diverse catchments.展开更多
Carbon dioxide（CO_2） capture and catalytic conversion has become an attractive and challenging strategy for CO_2 utilization since it is an abundant, inexpensive, and renewable C1 resource and a main greenhouse gas....Carbon dioxide（CO_2） capture and catalytic conversion has become an attractive and challenging strategy for CO_2 utilization since it is an abundant, inexpensive, and renewable C1 resource and a main greenhouse gas. Herein, a novel hydrazine-bridged covalent triazine polymer（HB-CTP） was first designed and synthesized through simple polymerization of cyanuric chloride with 2,4,6-trihydrazinyl-1,3,5-triazine. The resultant HB-CTP exhibited good CO_2 capture capacity（8.2 wt%, 0 °C, and 0.1 MPa） as well as satisfactory recyclability after five consecutive adsorption-desorption cycles. Such a polymer was subsequently employed as a metal-free heterogeneous catalyst for the cyclo-addition of CO_2 with various epoxides under mild and solvent-free conditions,affording cyclic carbonates with good to excellent yields（67%–99%） and high functional-group tolerance. The incorporation of hydrazine linkages into HB-CTP＇s architecture was suggested to play the key role in activating epoxides through hydrogen bonding. Moreover, HB-CTP can be reused at least five times without significant loss of its catalytic activity.展开更多
During the outbreak of coronavirus disease 2019(COVID-19),the identification of a SARS-CoV-2 infected case with untraceable epidemic origin has three values:(1)the region has community transmission of the virus;(2)a c...During the outbreak of coronavirus disease 2019(COVID-19),the identification of a SARS-CoV-2 infected case with untraceable epidemic origin has three values:(1)the region has community transmission of the virus;(2)a certain portion of population in the community is getting immunized and more individuals have already been immunized;(3)an unpredictable future risk exists for regions where there are no infected cases with untraceable epidemic origin.Minimizing or avoiding the aggregation infection through individuals with no clinical symptoms is crucial and possible as its occurrence is mainly attributed to the local environment as opposed to the super spreader with or without clinical symptoms.As infected cases are not necessarily positive with gene test by definition,proper application of gene test is crucial in the identification of asymptomatic cases.In the early stage of an outbreak of infectious disease,gene test can be used to identify asymptomatic cases but it should not be used to exclude cases with typical clinical symptoms and signs.In the middle or late stages of an outbreak gene test should be applied in evaluation of infection rate of the population of a region,in addition to be used in spreader identification and isolation.Although asymptomatic cases are attributed to the overwhelming effect of personalized defense against pathogens,they are still a source of infection.Asymptomatic cases are considered to be Qi deficiency and with lingering toxicity in traditional Chinese medicine(TCM).Treatment in such cases,typically,involves therapy focused on replenishing the Qi,tonifying the lung,clearing the fever,and detoxification in order to return to a normal health condition.The recommended Chinese medicines include Qing Fei Pai Du Decoction,Yi Qi Qu Du Decoction,Xuan Fei Bai Du Granule,Lian Hua Qing Wen Capsule(Granule),and Jin Hua Qing Gan Granule,etc.展开更多
文摘A fast, green and readily reproducible microwave-based method for the production of high quality silver nanoparticles （AgNPs） in high yield is presented. Starch is used as a stabilizing agent with few pentose different reducing carbohydrates as D-ribose, D-arabinose and L-arabinose. From the UV-vis peak profile spectra of the solutions of the silver nanoparticles, the authors have investigated the size of the NPs together with the average diameter, shape, and aggregation state of the colloidal AgNPs. TEM measurements and EDX analysis have confirmed the morphology of our AgNPs.
文摘First passage time in Markov chains is defined as the first time that a chain passes a specified state or lumped states. This state or lumped states may indicate first passage time of an interesting, rare and amazing event. In this study, obtaining distribution of the first passage time relating to lumped states which are constructed by gathering the states through lumping method for a irreducible Markov chain whose state space is finite was deliberated. Thanks to lumping method the chain＇s Markov property has been preserved. Another benefit of lumping method in the way of practice is reduction of the state space thanks to gathering states together. As the obtained first passage distributions are continuous, it may be used in many fields such as reliability and risk analysis
文摘With respect to the different hydrological responses of catchments, even the adjacent ones, in mountainous regions, there are a great number of motivations for classifying them into homogeneous clusters. These motivations include prediction in ungauged basins(PUB), model parameterization, understanding the potential impact of environmental changes, transferring information from gauged catchments to the ungauged ones. The present study investigated the similarity of catchments through the hydro-climatological pure time-series of a 14-year period from 2001 to 2015. Data sets encompass more than 13,000 month-station streamflow, rainfall, and temperature data obtained from 27 catchments in Utah State as one of the eight mountainous states of the USA. The identification, analysis, and interpretation of homogeneous catchments were investigated by applying the four approaches ofclustering, K-means, Ward, and SOM(Self-Organized Map) and a newly proposed Wavelet-Entropy-based(WE-SOM) clustering method. By using two clustering evaluation criteria, 3, 5, and 6 clusters were determined as the best numbers of clusters, depending on the method employed, where each cluster represents different hydro-climatological behaviors. Despite the absence of geographic characteristics in input data matrix, the results indicated a regionalization in agreement with topographic characteristics. Considering the dependency of the hydrological behavior of catchments on the physiographic field aspects and characteristics, WE-SOM method demonstrated a more acceptable performance, compared to the other three conventional clustering methods, by providing more clusters. WE-SOM appears to be a promising approach in catchment clustering. It preserves the topological structure of data which can, as a result, be proofed in a greater number of clusters by dividing data into higher numbers of distinct clusters withsimilar altitudes of catchments in each cluster. The results showed the aptitude of wavelets to quantify the time-based variability of temperature, rainfall and streamflow, in the way contributing to the regionalization of diverse catchments.
基金supported by the National Natural Science Foundation of China(21406025)the China Postdoctoral Science Foundation(2014M551067)the Start-Up Foundation of Dalian University of Technology(DUT13RC(3)58)~~
文摘Carbon dioxide（CO_2） capture and catalytic conversion has become an attractive and challenging strategy for CO_2 utilization since it is an abundant, inexpensive, and renewable C1 resource and a main greenhouse gas. Herein, a novel hydrazine-bridged covalent triazine polymer（HB-CTP） was first designed and synthesized through simple polymerization of cyanuric chloride with 2,4,6-trihydrazinyl-1,3,5-triazine. The resultant HB-CTP exhibited good CO_2 capture capacity（8.2 wt%, 0 °C, and 0.1 MPa） as well as satisfactory recyclability after five consecutive adsorption-desorption cycles. Such a polymer was subsequently employed as a metal-free heterogeneous catalyst for the cyclo-addition of CO_2 with various epoxides under mild and solvent-free conditions,affording cyclic carbonates with good to excellent yields（67%–99%） and high functional-group tolerance. The incorporation of hydrazine linkages into HB-CTP＇s architecture was suggested to play the key role in activating epoxides through hydrogen bonding. Moreover, HB-CTP can be reused at least five times without significant loss of its catalytic activity.
基金funding support from the Major Project on Prevention and Treatment of COVID-19 with TCM of Hunan TCM Bureau(No.KYGG06)the Special Project of Changzhutan National Independent Innovation Demonstration Zone of Hunan Province(No.2018XK2106)。
文摘During the outbreak of coronavirus disease 2019(COVID-19),the identification of a SARS-CoV-2 infected case with untraceable epidemic origin has three values:(1)the region has community transmission of the virus;(2)a certain portion of population in the community is getting immunized and more individuals have already been immunized;(3)an unpredictable future risk exists for regions where there are no infected cases with untraceable epidemic origin.Minimizing or avoiding the aggregation infection through individuals with no clinical symptoms is crucial and possible as its occurrence is mainly attributed to the local environment as opposed to the super spreader with or without clinical symptoms.As infected cases are not necessarily positive with gene test by definition,proper application of gene test is crucial in the identification of asymptomatic cases.In the early stage of an outbreak of infectious disease,gene test can be used to identify asymptomatic cases but it should not be used to exclude cases with typical clinical symptoms and signs.In the middle or late stages of an outbreak gene test should be applied in evaluation of infection rate of the population of a region,in addition to be used in spreader identification and isolation.Although asymptomatic cases are attributed to the overwhelming effect of personalized defense against pathogens,they are still a source of infection.Asymptomatic cases are considered to be Qi deficiency and with lingering toxicity in traditional Chinese medicine(TCM).Treatment in such cases,typically,involves therapy focused on replenishing the Qi,tonifying the lung,clearing the fever,and detoxification in order to return to a normal health condition.The recommended Chinese medicines include Qing Fei Pai Du Decoction,Yi Qi Qu Du Decoction,Xuan Fei Bai Du Granule,Lian Hua Qing Wen Capsule(Granule),and Jin Hua Qing Gan Granule,etc.
